Self-retightening clamps are required to avoid the so-called "cold-leak" problems which occur when the nipples warm up and therefore expand, thereby causing an increase in the hose diameter and when the nipples thereafter again cool off, thereby causing again a decrease in the hose diameter. Such self-retightening clamps are of importance in particular with diesel trucks, buses, tractors, large volumetric internal combustion engines and the like in which the fluid medium such as water or oil flowing through the hoses and nipples, undergoes alternate warm-up and cooling-off. To avoid "cold-leak", the clamp(s), after expansion thereof, must again be able to automatically contract to assure again tightness of the hose connection. Furthermore, if self-retightening clamps are used, it is no longer necessary to utilize only thick-walled rubber hoses in order to obtain a certain spring action in the rubber. However, though such thick-walled rubber hoses are capable of a limited breathing, they cannot avoid "cold-leak" without the then normally required retightening. Self-retightening clamps are additionally very important because they can also be used with aluminum and plastic nipples which undergo considerably larger changes in diameter than those made of steel. Furthermore, a hose connecting system utilizing self-retightening clamps will allow the use of thin-walled hoses which are more favorable from a cost point of view and additionally offer the advantage of being more flexible and more easy to handle by the assembly personnel. As is also known, the "cold-leak" problems become even more severe in cold climate, especially during the winter, when many truckers keep the truck engines running to prevent leakage of coolant.
Screw-type clamps with a clamping surface devoid of any discontinuities, gaps or steps are known from FIG. 2 of my prior U.S. Pat. No. 4,521,940 which also offer an automatic retightening by the interposition of a spring 44. The clamps disclosed in this prior patent enjoyed substantial commercial success owing to their ability to assure tightness of the hose connection under widely differing temperatures and pressures. However, some problems were encountered in the use of these clamps due to the large tolerances encountered with the hose connections for which these screw-type clamps were nominally designed. More particularly, as with other clamps, the screw-type clamps as disclosed in my aforementioned patent are manufactured in different discrete nominal sizes corresponding to the maximum hose diameter for a given hose size as used in the industry. Different nominal sizes can be realized with my prior clamps by changing the clamping band length without substantial change in the basic clamp structure. Each size of commercially available screw-type clamps embodying the invention of my aforementioned patent thereby provides limited adjustment in the diametric dimension to compensate for a limited tolerance range in the outer dimensions of the hose. This is achieved by the presence of a limited number of apertures in the separate band part to vary the effective length and therewith the diametric dimension of the clamp by selective engagement in these apertures by outwardly extending hooks fixedly positioned in the clamping band. However, the external dimensions of hoses supplied by manufacturers involve at times a tolerance range beyond the adjustment capability of these prior art screw-type clamps. This then necessitated a shut-down of the assembly line because the operator on the assembly line had to use a different size clamp on the same hose.
Another drawback encountered with the screw-type clamps according to my aforementioned patent involved the necessity to pack the clamps individually in bags so as to preclude that the separate clamping band part would swing out laterally. This, in turn, increased the cost of the clamps due to increased labor and materials.